ISO containers are standardized with respect to their dimensions and are provided with corner fittings at all of their corners. Corresponding locking members such as pins or twist-locks are disposed at predetermined spacings on platforms of container transport vehicles. The largest ISO containers have a length of 40 ft. (12192 mm).
For the transport of low-density materials such as gases including pressure-liquified gases, more recent draft standards (such as the draft CEN Swap Tank Euro Standard) provide for--normally symmetrical--extensions of the tank beyond the standard length of the base frame structure, which is standardized at 20 ft. (6058 mm), 30 ft. (9125 mm) or 40 ft. (12192 mm) for ISO containers. In order to secure such extended tanks on the available vehicle platforms, the transverse bars provided with corner fittings are maintained at their standard spacing and the tank symmetrically projects beyond these transverse bars. In many cases, a manhole concentric with respect to the tank axis is disposed in the tank bottom on one of the projecting end regions.
For protecting the tank end regions including any manhole armatures that may be provided there, it has been known to dispose attachments outside the transverse bars which slightly project beyond the tank in the longitudinal direction thereof and are formed of bent tubes like railings or include straight bars and struts that may be interconnected by means of additional outer ISO corner fittings. Such attachments may further be reinforced by disposing two such structures above each other.
U.S. Pat. No. 4,603,788 discloses a swap tank which comprises a cylindrical main portion having curved tank bottoms, base frame structures associated to the tank ends and each including a transverse bar and a pair of diagonal struts extending from the ends of the transverse bar towards each other, and two saddle arrangements each including a support member disposed between the tank bottom and the associated base frame structure. The end regions of the tank are thus provided with structures that transmit the forces exerted on the tank to support and engagement points (corner fittings) of transverse bars provided at the tank ends. The document, however, describes a tank which is sized to fall completely within the standard dimensions, each the end frame being each provided with four corner fittings defining the outer dimensions of a tank container.
German Offenlegungsschrift 3,714,396 further discloses a connection between the tank and framework of a tank container which includes two parallel and somewhat triangular sheet metal pieces. Otherwise however the known design is quite dissimilar from the present invention as regards both the underlying object and the structure meeting that object.